A gel (G) which contains a component of a catalyst is prepared. The gel (G) and another gel (GA) are arranged in layers at a position which faces open ends (2ao) of exhaust flow passages (2a) of a wall flow-type particulate filter (1). Next, a pusher (P) is used to push and pack the gel (G) and other gel (GA) through the open ends (2ao) to the insides of the exhaust flow passages (2a). Next, the particulate filter (1) is made to dry to thereby make the partition walls (3) carry the catalyst on their surfaces or in their micropores.